1. Field of the Invention
The present invention relates generally to network systems. In particular, the present invention relates to energy consumption in a network system.
2. Description of the Related Art
A network system, or a distributed system typically contains a plurality of nodes. Multiple network buses, such as high-speed serial buses, are normally used to connect between the nodes. Each node usually contains at least one device, which performs certain functions. Typical devices include, but are not limited to, personal computers, Internet servers, printers, telephones, scanners, et cetera.
With increasing performance of each device, higher performance of network buses, such as serial buses, is often required. A typical example of commercially available high performance bus is IEEE (xe2x80x9cInstitute of Electrical and Electronics Engineerxe2x80x9d) 1394-1995 and its supplements: IEEE 1394a and P1394b, which are developed by an IEEE working group. One common problem with high-speed serial buses currently used in distributed systems is power consumption.
An active node on a distributed system contains at least one active device, and it typically consumes power regardless of whether the device is in use or not in use. For example, a printer consumes power even though it is not printing.
To reduce power consumption, a method of suspending idle nodes has been employed. This method suspends a node if the node is not in use and resumes the suspended node when it is needed. When a node is suspended, its node-ID (xe2x80x9cnode identificationxe2x80x9d) is typically no longer valid in the bus topology. Similarly, when a node is resumed, a new node-ID has to be added. Accordingly, a bus reset is required when a node is suspended. For the same reason, a bus reset is also needed if a suspended node is resumed. However, bus reset takes time and resources because each bus reset must re-establish a new root node, set up new node-IDs, negotiate a bus manager, and enumerate unit functions on the bus.
A leaf node is, in one embodiment, switched to a standby state in response to a standby command. A leaf node self-identification (xe2x80x9cself-IDxe2x80x9d) packet is synthesized in response to leaf node information, which is stored in a parent node. The leaf node self-ID packet is transmitted from the parent node in response to a request.
Additional features and benefits of the present invention will become apparent from the detailed description, figures and claims set forth below.